Henry harris



Reissued Jan. 22, 1924.

UNITED STATES Re. 15,751 PATENT OFFICE.

HENRY HARRIS, OF LONDON, ENGLAND.

nnzmcme LEAD.

Ho Drawing. Original No. 1,395,820, dated November 1, 1921, Serial No.354,851, filed. January 29, 1920.

Serial No. 665,236.

DIVISION B.

To all whom it may concern:

Be it known that I, HENRY HARRIS, a subject of the King of GreatBritain, residing in London, England, have invented certain new anduseful Improvements in Dezincing Lead, of which the following is aspecification. 7

Several rea ents have been suggested for dezincing lea among themcaustic soda; this reagent, however, is not particularly active andparts with sodium to the lead. A mixture of zinc chlorid and litharge iseffective, but the lithar'ge must be free from silver and thereforeexpensive and a considerable amount of the zinc chlorid volatilizes andis lost at the temperature of the molten lead. It has also been proposedto utilize a double salt of zinc chlorid. with the litharge or with leadsulphide ore in a process where the quantity of litharge or leadsulphide ore used must be such that the amount of lead contained thereinis at least. chemicall equivalent, to the zinc in the metal to bepurified; that is to say the lead contained in the litharge or sulphideore must be in the ratio of about 207 parts of lead to each 65 parts ofzinc contained in the lead to be I urified. (See German Patent 241483.)This ast process is also objectionable because of the expense ofproducing the necessary amount of litharge or sulphite ore freefromsilver and other impurities.

I have found that fused alkali chlorid will react with molten leadcontaining zinc to remove the latter from the lead. The

temperature required, however, is so, high I exoeedin 500 0., moltenlead containing me can to such an extent as 'to render unnecessary theaddition of other oxygen (or a source of oxygen) for the dezincmg.

oxidized by atmospheric oxygen With these objects in view my inventionin one aspect comprises as the reagent the use of a mixture of alkalichlorid with another compound or compounds of an alkali metal, whichwill reduce the melting point of the alkali chlorid, such for example,as caustic alkali, either with or Without an addition of oxygen (or asource of oxygen) other than thatderived from atmospheric oxidization,and also comprises the conducting of the dezincing at the reducedtemperature, referably below that where any apprecia le amount of alkalimetal passes permanently into the lead.

A mixture of caustic alkali and alkali chlorid is particularly usefulsince the mixture does not part with sodium to the lead at thetemperature at which it can be used, and the reaction which removes thezinc is not dependent on oxygen other than that contained in the mixturedue, I believe, to the capacity of the mixture to absorb oxygen whensaid mixture and molten lead are mixed although oxygeli' added inthe'form of relatively small quantities of lithrage or forced air mayhasten the process.

In another aspect my invention comprises, with the maintaining of therelatively low temperature, the use of zinc chlorid and alkali chloridas the reagent, with or without an addition of oxygen (or a source ofoxygen) other than that derived from atmospheric'oxidization; but in thecase of an added source of'oxygen this phase of my invention doesnotcontemplate or include a proces where the ox gen source is lead oxideor an ore of lead oxide, used in such quantity that the contained leadis in amount chemically equivalent to the zinc in the metal to bepurified; that is to where a process is carried out'dependin upon thisrelatively large amount of lea oxide in conjunction with the zincchlorid and sodium chloridfor thev dezincing operation, as that processis known. This second aspect of my invention, does, however, not excludethe use of relatively small amounts of lead oxide such as one may haveon hand or ma desire to reduce to metallic lead and which may beregarded asfincidental tobut not necessary for the carrying out of mydezincing process- As in the case ofthe caustic alkali in the but itsefl'ectivenes's may be improved whenthe addition of oxygen (or a sourceof oxygen) is not objectionable.

In this case the mixture is more efi'ective than the known reagentconsisting of zinc chlorid and litharge alone and less costly in zincchlorid since the latter does not volatilize so readily when used inconjunction with alkali ch orid. This phase of my invention is also moreefl'ective than the known procew utilizing a mixture of litharge, zincchlorid and sodium chlorid and requiring litharge in such quantities asto contain lead in an amount at least chemically equivalent to the zincin the metal to be purified.

I will further describe my invention by giving certain examples of themanner in which it may be practiced, and the invention will thereafterbe more particularly. pointed out in the appended claims.

The following examples illustrate the invention:'

(1) A mixture of 24 lbs. of sodium chlorid and 25.5 lbs. of caustic sodais brought.

into intimate contact (such as by the method described in my applicationfor U. S. patent Serial No. 354,852) with 4 tons of lead containing 0.65per cent of zinc, heated to about 500 C. The zinc is chloridized andoxidized and is found as a scum or dross mixed with the rea nt.

(2) The lead to e dezinced is brought into intimate contact at a.temperature about 500 (3., with the double chlorid of zinc and sodiumamountin to 3.6 times the weight of the zinc contalned in the lead. Air15 either blown through, the lead during the operation or supplied inthe manner described in my said application for. U. S. Patent Serial No.354,852- The oxidized and chloridized zinc is removed as referred toin'example 1. The reagent is not ex hausted by a single treatment andmay be used again.

In my co-pending re-issue application Sr.

No. 665,235 I aim to cover that phase or said invention and the bestmeans Iknow of carrying the same into practical effect,

1. Process of dezincinglead which comprises bringing the molten leadintointimate contact .With a mixture comprising alkalito exceed about 500(3., maintaining, the mixture not to exceed said temperature andconducting the operation without the addition of lead oxide (or orecontaining lead V oxide) in such quantity that the" contained lead is inamount chemically eguivalent. to

the zinc in themetalto be puri ed.

2. Process of dezincing lead which comprises bringing the molten leadintointimate contact with a mixture comprising alkali chlorid and asubstance which lowers the melting point of the alkali chlorid so asnotto exceed about 500 (3., maintaining the mixture not to exceed saidtemperature and conducting the operation without depending upon theaddition of lead oxide for the dezincing reaction.

3. Process of dezincing lead which comprises bringing the molten leadinto intimate contact with a mixture comprising an alkali chlorid and asubstance which lowers the meltin point of the alkali chlorid so as notto exceed about 500 C.,maintaining the mixture not to exceed saidtemperature and conducting the operation in such manner as to 'efiectatmospheric oxidization for the dez'incing reaction, so as to be able todispense partially or wholly with the addition of lead oxide (or orecontaining lead oxidell.

4. recess of dezincing lead which comprises bringing the molten leadinto intimate contact with a mixture comprising alkali chlorid and zincchlorid at a temperature not exceeding about 500 C., maintaining themixture not to exceed said temperature and conducting the operationwithout the addition of lead oxide (or .ore containing lead oxide) insuch quantity that thecontained lead is in amount chemically equivalentto the zinc in the metal to be purified.

5. Process of dezincing lead which com prises bringing the molten leadintointimate contact with a mixturecomprising alkali chlorid and zincchlorid at a temperature not exceeding about 50030., maintainingthemixture not to exceed said temperature and conducting the operation insuc manner as to effect atmospheric oxidiza tion for the dezincingreaction, and without depending upon lead oxide .(or ore con- 113111111lead oxide) for said reaction.

6. rocess of dezincing lead which comprises bringing the molten leadinto intimate contact with a molten. mixture com prising sodium chloridand at least a sufcient amount of a substance which will act to reducethe melting point of the sodioxidization for the dezincing reaction 50as um chlorid to reduce the meltin point of tube able to dispensepartially or wholly the mixture substantially below t at of the with theaddition of lead-oxide (or-ore, con- 1. sbdium chlorid, maintainin themixture taining. lead oxide). i a

5 substantially below the me ting point of In testimony whereof I havesigned my the sodium chlorid, and conducting theopername to thisspecification. a 3 1 ation in such manner as to efl'ectatmospheric VHENRY HARRIS.

